pep itpa working group on rmp elm control: 11 status...

M.E. Fenstermacher - Status of Progress on Work Plan in PEP ITPA WG on RMP ELM Control 1

PEP ITPA Working Group on RMP ELM Control: 11th Status Report on Work Plan Progress

M.E. Fenstermacher (chair) M. Becoulet, P. Cahyna, C.S. Chang, T.E. Evans, X. Gao, Y. Jeon, A. Kirk, Y. Liang, A. Loarte, R. Maingi, O. Schmitz, Y. Sun, W. Suttrop, G. Xu, S. Yoon, (members),

R. Maingi (PEP ITPA chair)

Contributors: A. Briesemeister, K. Burrell, J. Callen, M. LeConte, E. Hinson, A. McLean, M. Valovic

ITPA Pedestal and Edge Physics WG Meeting

IPR, Ahmedabad, India, March 16-18, 2016


Operation at AUG, DIII-D, EAST, JET and KSTAR since Garching (Oct 2015) PEP Meeting

•  AUG, COMPASS, DIII-D, EAST, JET, KSTAR and NSTX-U will all run experiments in the next 6 months

CMOD

AUG

COMPASS

DIII-D

EAST

JET

KSTAR

MAST-U

NSTX-U

???


2015 RMP ELM Control Work Plan •  Main Sections

–  1.0 Experiments on ELM Suppression or 30x Mitigation

–  2.0 Experiments on Compatibility Issues

–  3.0 Theory of ELM Suppression/Mitigation Physics Mechanisms

–  4.0 Theory of Pedestal and Transport Effects

–  5.0 ITER Prediction

•  Timelines should be discussed and updated

–  ITER Coil Specifications Re-examination

DONE AUG + DIII-D

DONE ? DONE ?


PEP Joint Experiments Contribute to RMP ELM Control Work Plan Objectives 1 and 2

•  PEP-19: Basic mechanisms of edge transport with resonant magnetic perturbations in toroidal plasma confinement devices

–  Proposed to close at the end of 2015

–  Final report in progress

•  [PEP-34 Non-resonant magnetic field driven QH Mode (DIII-D only for now)]

•  PEP-38: Access conditions for ELM mitigation and ELM suppression by magnetic perturbations at low pedestal collisionalities –  Contacts: W. Suttrop (AUG) chair, R. Nazikian (DIII-D), Y. Sun (EAST),

Y. M. Jeon (KSTAR), A. Kirk (MAST-U)

–  Provides input to work plan objectives 1 (ELM Suppression or Mitigation) and 2 (Compatibility Issues)

–  Significant progress since October meeting


Sup/Mit: In Both Low and High Collisionality Plasmas on Multiple Devices •  Sup/Mit for multiple conditions on different devices using internal coils

Device n# Coil Rows

ν* Triangularity Res, Parity, Δq95 Sup/Mit

AUG 1 2 High Low Both, None Sup/Mit

AUG 1 2 Low-Mod Low Res, High q95, Rot braking Mit (2x)

EAST 1 2 Mod-High Moderate Res, High q95=5, Rot braking Mit (5X)

KSTAR 1 3 Moderate Moderate Res,+90deg, q95= 5, 6, 7.5 Sup

KSTAR 1 3 Moderate High Res,+90deg, >6 - 6.5 Sup

KSTAR 1 3 Moderate High Res,+0deg, >6 - 6.5 Mit


AUG 2 2 High Moderate Both, None Sup/Mit


AUG 2 2 Low Low Res shifted from vac, pumpout, phase dep

Mit (5x)

AUG 2 2 Moderate Low Res shifted from vac No Effect


Sup/Mit: In Both Low and High Collisionality Plasmas on Multiple Devices

•  Sup/Mit for multiple conditions on different devices using internal coils

Expts Sup/Mit

Device n# Coil Rows


AUG 2 2 Moderate Low Not phase sensitive, no pumpout

Mit (10x) or ELM-free

AUG 2 2 Low, ν*=0.15

Low Lower, High Upper

Clear pumpout, kink res Δϕ=90deg, intact Te, Ti,

Sup !!

COMPASS 2 2 High Low Res, even parity, pumpout Mit (1.5x ?)

DIII-D 2 2 Low ISS Res, 60deg, 3.5 – 3.6 Sup

DIII-D 2 2 Low ISS Res, continuously varied, 4.1

Sup or Mit vs phase

EAST 2 2 High Moderate Non-res, q95 ~ 4.6 Mit (5-8x)

KSTAR 2 1 or 3 Moderate High Res,+90deg, >3.5 - 4 Sup

KSTAR 2 3 Moderate High Res,+90deg, >4 - 5 Mit

MAST 2 1 Moderate Moderate, LSN One row, Rotation braking Mit (1.5x)




Expts Sup/Mit

Device n# Coil Rows


DIII-D 3 2 High Moderate NonRes, Odd, 3.5 – 3.6 Sup

DIII-D 3 2 High High Non-Res, Odd, 3.5 – 3.6 Sup/Mit

DIII-D 3 2 High Low Non-Res, Odd, 3.5 – 3.6 Mit

DIII-D 3 2 Low Low Res-Even, 3.5 – 3.6, Sup

DIII-D 3 1 or 2 Low ISS Res, Even, 3.3 – 3.7, 7-7.2, 3.15 (One row)

Sup

DIII-D 3 2 Low ISS Res & Non-res, 3.5-3.6, Simulate loss of coils

Sup

DIII-D 3 2 High ITER Baseline Res and non-res, q95 = 3.1, Low Torque 1 Ntm

Mit (2x)

DIII-D 3 2 Low ITER Baseline Res and Non-res, q95 = 3.1, Mod Torque>3.5 Ntm

Supp

DIII-D 3 2 Low Low Upper Res-Even, 3.5 – 3.6, Sup

DIII-D 3 2 Low ASDEX Shape Res-Even, 3.5 – 3.6, Sup




Expts Sup/Mit

Device n# Coil Rows ν* Triangularity Res, Parity, Δq95 Sup/Mit

EAST 3 2 High Moderate Non-res, Mit (1.5x)

MAST 3 2 Moderate High CDN Res, Even, 7.2 Mit (9x)

AUG 4 2 or upper High Low Non-Res, Even, None Sup/Mit

EAST 4 2 High Moderate Non-res, even, q95=4.4 Mit (2.5x)

MAST 4 1 Low-High Moderate One row Mit (5x)

MAST 6 1 Low-High

Moderate One row Mit (5x)



•  Sup/Mit for multiple conditions on different devices using external coils

Device n# Coil Rows ν* Triangularity Res, Parity, Δq95 Sup/Mit

JET-C 1 1 Low Low One row, LM threshold Mit (10x)

JET-C 2 1 Low Low One row, LM threshold Mit (5x)

JET-C 2 1 High (ILW)

Low One row, Rot braking Mit (5x)

JET-C 2 1 Low (ILW)

Low One row, Rot braking Mit (4x)

JET-ILW 1 1 Low Moderate High upper δ, ILW Mit (>10x)

JET-ILW 1 1 Low Low Low δ “Slim”, ILW Mit (<2x)

MAST 2 1 Moderate High CDN One row Mit (8x)

NSTX 3 1 High Moderate One row Triggering

Expts Sup/Mit


Sup/Mit: In Both Low and High Collisionality Plasmas on Multiple Devices – Near Term Planned Experiments


Expts Sup/Mit

Device n# Coil Rows


AUG 3 2 Low Low Lower, High Upper

Res, some n=2 and n=4, PEP-38 shape, q95 = ??

DIII-D 3 2 Low High Res, Low Torque, ITER Baseline scenario (q95~3.5 to match coils)

DIII-D 3 2 Low High near DN Res, Steady State Hybrid core

DIII-D 3 2 Low High Non-Res, Vary poloidal mode spectrum dynamically to spread heat flux

KSTAR 1,2 3 Moderate High Misalignment (under ELM-controlled status) that may distribute the peak heat loads,

KSTAR 1,2 3 Moderate High Switching of low-n RMPs in the middle of run (under greatly mitigated/suppressed status)


Planned Experiments on DIII-D and KSTAR Address Urgent ITER RMP Issues

•  AUG: ELM Suppression, low ν*, with n=3 RMP in PEP-38 shape by end of May

•  DIII-D RMP experiments to be completed by mid-April –  RMP ELM Control in ITER baseline scenario at low torque

•  Focus on low input torque, low toroidal rotation plasmas •  Work at q95 ~ 3.5 optimized for DIII-D I-coil n=3 even parity configuration

–  RMP ELM suppression with steady state hybrid core at low rotation •  Hybrid core with q0 > 1 using continuous 3/2 mode •  Steady state (Vloop ~ 0) sustained by ECCD and NBCD •  RMP ELM suppression with n=3 odd parity (better resonance at high q95)

–  RMP ELM suppression with dynamic heat flux deposition •  ELM suppression in ISS with n=3 at low collisionality •  Ramp quartets of I-coils separately to test response vs. vacuum calculations •  Ramp combinations of quartets for n=3 à n=1 à n=3 variations

•  KSTAR experiments to be completed before IAEA –  Misalignment (with ELM-controlled status): may distribute peak heat loads –  Switching of low-n RMPs in the middle of run (under greatly mitigated/

suppressed status)


Experiments: ELM Suppression or 30x ELM Peak Heat Flux Mitigation (Sup/Mit)

Suppression or 30x Mitigation (Sup/Mit): ü 1.2 In dimensionless similarity

discharges with comparable RMP spectra on two or more devices –  NEW: ELM Suppression obtained in DIII-D

plasmas with step-wise AUG shaping: •  Started with ISS, n=3 •  Reduced upper triangularity

–  Little effect on suppression –  Some evidence of multiple q95

windows in q scan •  Reduced lower triangularity

–  Needed to condition outer shelf to maintain low nu* w/o pump and high vtor

–  New AUG n=3 expt planned Expts Sup/Mit

Loarte NF2013

Kirk IAEA 2014

EAST


Title

•  ??

Suttrop, Kirk, Nazikian, PEP-38


Title

•  ??




Suppression or 30x Mitigation (Sup/Mit): ü 1.1 In both low and high collisionality

(density) plasmas on multiple devices –  NEW: AUG SUPPRESSION with n=2 at

conditions matching DIII-D suppression •  Low nu* ~ 0.15 •  Increased upper triangularity •  Optimal upper-lower coil phasing •  New n=3 expt planned

–  Oct mtg: AUG best mitigation at low (<~ 0.4) collisionality for maximized edge kink-peeling response, pumpout

–  Oct mtg: EAST mitigation with n=1, 2, 3, and 4 at high collisionality

–  Oct mtg: COMPASS H-mode, pumpout, fELM increase

Expts Sup/Mit

Loarte NF2013

Kirk IAEA 2014

EAST


Title

•  ??



•  ???



Title

•  ??? Suttrop, Kirk, Nazikian, PEP-38


Title

•  ???



TItle

•  ???




Suppression or 30x Mitigation (Sup/Mit): •  1.3 With minimal pedestal density pumpout at low collisionality on

multiple devices –  NEW: AUG refuels pedestal with pellets, ELM freq increased, confinement

and Teped unchanged by pellets

–  Oct mtg: DIII-D RMP feedback reduces pumpout, suppression retained

•  1.4 At ITER baseline q95 in multiple devices –  Oct mtg: DIII-D ELM Suppression at 5 Nm torque with ITER baseline

shape and q95=3.1 but only mitigation below 3.5 Nm torque – New DIII-D expt planned

•  1.5 At ITER low input torque in multiple devices –  Oct mtg: DIII-D sees only ELM mitigation when using ITER baseline

shape, q95=3.1 and low input torque (1 Nm close to ITER scaled torque=0.35 Nm) New DIII-D expt planned

Expts Sup/Mit


???

•  ??? Valovic



Suppression or 30x Mitigation (Sup/Mit): •  1.3 With minimal pedestal density pumpout at low collisionality on

multiple devices –  NEW: AUG refuels pedestal with pellets, ELM freq increased, confinement


–  Oct mtg: DIII-D RMP feedback reduces pumpout, suppression retained

•  1.4 At ITER baseline q95 in multiple devices –  Oct mtg: DIII-D ELM Suppression at 5 Nm torque with ITER baseline

shape and q95=3.1 but only mitigation below 3.5 Nm torque – New DIII-D expts planned

•  1.5 At ITER low input torque in multiple devices –  Oct mtg: DIII-D sees only ELM mitigation when using ITER baseline

shape, q95=3.1 and low input torque (1 Nm close to ITER scaled torque=0.35 Nm) - New DIII-D expts planned

Expts Sup/Mit


Experiments: Determine Compatibility Of ELM Suppression or 30x Mitigation With ITER Operation Constraints

Experiments: ITER Compatibility Issues •  2.1 Determine impact of Sup/Mit on peak divertor power load

–  Oct mtg: AUG fine stepwise rotation maps out heat flux fingers

•  2.2 Explore impact of rotating RMP for power load spreading - Sup/Mit –  NEW: Vacuum calculations to optimize (minimize) required coil current

swings necessary to spread peak heat flux in DIII-D - New DIII-D and KSTAR expts planned

•  2.3 Sup/Mit close to LH threshold power –  Oct mtg: DIII-D ELM suppression in He plasma close to L-H threshold with

ECH and balanced NBI – New DIII-D expt planned to repeat in D2

•  2.4 Sup/Mit with low core accumulation of metal impurities –  NEW: DIII-D: effect of RMP structures on W erosion/re-deposition L-mode,

WI emission similar to Lc during 3D heat/particle flux sweep over DiMES

–  Oct mtg: DIII-D F-transport in ELMing, RMP suppressed and QH-mode

Expts Compatibility



Experiments: ITER Compatibility Issues •  2.5 Determine compatibility of Sup/Mit with radiative divertor for steady-state

heat load reduction –  NEW: During RMP 3D structure of SOL/divertor Te measured in attached

conditions similar to EMC3-Eirene predictions; reduced structure seen when detached

–  Oct mtg: DIII-D high ν* ELM mitigation outer heat flux lobes between ELMs eliminated at high density detached divertor

•  2.6 Determine impact of Sup/Mit on LH threshold power •  2.7 Sup/Mit during current ramp (varying q95)

–  NEW: ELM suppression in DIII-D with hybrid core less sensitive to q95

•  2.8 Sup/Mit in helium plasmas

–  Oct mtg: DIII-D He plasma, moderate beta (He NBI) - New expt planned

•  2.9 Determine compatibility with pellet fueling –  NEW: AUG refuels pedestal with pellets, ELM freq increased, confinement


Expts Compatibility


3D Structure of DIII-D SOL/Divertor Te Measured With TS in Attached Conditions With RMP Applied

•  RMP induces lobe structure in 2D Te data from Thomson scattering at low density, ne/nGW = 0.4 –  Filtered for end of ELM cycle –  Data from radial sweep mapped

to single EFIT •  Assumes rigid structure

motion

Briesemeister, McLean PSI16


3D Structure of DIII-D SOL/Divertor Te, pe During RMP at Low Density But Not at High Density

•  Te reduced and no lobe structure in Te and pe at high density, ne/nGW = 0.7

Briesemeister, McLean PSI16

nGW = 0.4 Attached

nGW = 0.7 Partially Detached

pe

pe Te

Te



Experiments: ITER Compatibility Issues •  2.5 Determine compatibility of Sup/Mit with radiative divertor for steady-state

heat load reduction –  NEW: During RMP 3D structure of SOL/divertor Te measured in attached

conditions similar to EMC3-Eirene predictions; reduced structure seen when detached

–  Oct mtg: DIII-D high ν* ELM mitigation outer heat flux lobes between ELMs eliminated at high density detached divertor

•  2.6 Determine impact of Sup/Mit on LH threshold power •  2.7 Sup/Mit during current ramp (varying q95)

–  NEW: ELM suppression in DIII-D with hybrid core less sensitive to q95

•  2.8 Sup/Mit in helium plasmas

–  Oct mtg: DIII-D He plasma, moderate beta (He NBI) - New expt planned

•  2.9 Determine compatibility with pellet fueling –  NEW: AUG refuels pedestal with pellets, ELM freq increased, confinement


Expts Compatibility


Title

•  ???

R. Nazikian, PedELM mtg, 3/2/16

Nazikian



Experiments: ITER Compatibility Issues

•  2.10 Optimize for minimum degradation from ELMing H-mode pedestal pressure, density and temperature

–  Oct mtg: DIII-D phase flip pumpout/pumpin first appears where veperp =0

•  2.11 Determine effect on fast particle confinement: beam ions / alphas –  Oct mtg: DIII-D FILD data (5.7% NB ion loss, increased divertor heat flux)

validates SPIRAL (Full Orbit) + M3D-C1 (plasma response) simulations

Expts Compatibility


Theory (Experimental Validation): ELM Suppression/Mitigation Physics Mechanisms

Theory coupled with experimental validation to:

ü 3.1 Determine dependence of penetration / screening on RMP spectral components, plasma rotation, dominance of Xpt displacement

–  NEW: AUG n=2 ELM Suppression with 90 deg phasing calculated by MARS-F as optimum for edge kink plasma response

–  Oct mtg: AUG strongest mitigation when edge kink-peeling plasma response (top/bottom of plasma) at 90 deg phasing

•  Consistent with DIII-D (HFS magnetics response) and MAST (maximize Xpt/midplane displacement)

M.E. Fenstermacher - Status of Progress on Work Plan in PEP ITPA WG on RMP ELM Control 34 Suttrop ITER IO 7/2015



Theory coupled with experimental validation to: ü 3.2 Determine if plasma response is Kink-like or Island-like structure

–  Oct mtg: AUG, DIII-D, MAST and simulations (M3D-C1, MARS-F, JOREK) emerging picture (Moyer SFP) connecting mitigation and suppression:

•  v_perp_e ≠ 0 edge kink-peeling plasma response (strongest near Xpts) leads to mitigation – optimized if applied spectrum aligned with kink

•  At v_perp-e = 0 bifurcation to penetrated (amplified?) fields and tearing response (measure strong HFS response) can lead to suppression

•  Mitigation seen if tearing too far in to limit pedestal expansion below ELM limits, suppression as tearing zone moves out due to transport

•  3.3 Understand the role of proximity of betaped to betacrit in plasma response




•  3.4 Determine physics mechanism for transport (esp. particle) induced by self-consistent magnetic perturbation – Many Candidates

M.E. Fenstermacher - Status of Progress on Work Plan in PEP ITPA WG on RMP ELM Control 37 Evans ITER IO 7/2015




•  3.4 Determine physics mechanism for transport (esp. particle) induced by self-consistent magnetic perturbation –  NEW: Callen – Tokamak Forced (induced by ELM crash) Reconnection

Model (FRM) yields formulas for bifurcation phenomena seen in DIII-D n=2 experiments (Nazikian, Paz-Soldan PRLs) that match data within ~ 2x.

•  Necessary condition on electron flow freq (veperp) for field penetration

•  Sufficient condition for applied field strength so that RMP-induced torque exceeds 2D equilibrium torque

•  Timescale for bifurcation •  Magnetic flutter transport supports observed flattening of ne and Te,

and density pumpout •  Low collisionality required for flutter transport consistent with expt •  Strong flutter transport requires well spaced rational surfaces and

strong kink response half way between rationals à q dependence C. Paz-Soldan et al.,, Phys. Rev. Lett. 114, 105001 (2015). R. Nazikian et al., Phys. Rev. Lett. 114, 105002 (2015).


ELM Suppression via Forced Magnetic Reconnection


•  3.4 Determine physics mechanism for transport (esp. particle) induced by self-consistent magnetic perturbation – Many Candidates

–  NEW: Callen – Toroidal Forced Reconnection Model to explain bifurcation phenomena seen in DIII-D n=2 experiment (Nazikian, Paz-Soldan PRLs)




•  3.4 Determine physics mechanism for transport (esp. particle) induced by self-consistent magnetic perturbation

–  NEW: LeConte – Equilibrium Er reduced by RMPs through “resonant current” coupling to Vortex Flows (patterns seen in RFX-Mod and TEXTOR)

•  Since “resonant currents” involved, sensitive to q-profile (q95)

•  Implies resonant braking of toroidal rotation by RMPs

–  Oct mtg: LeConte – δBr from magnetic perturbations (MPs) can induce coupling of Zonal Flow (ZF) energy to Vortex Flow (VF) (long lived convective cells)

•  Either get ZF damping or spatial resonance depending on MP phase •  VF energy scales as (δBr/B)1.9 •  VF flow pattern slow to form after RMP on




•  3.4 Determine physics mechanism for transport (esp. particle) induced by self-consistent magnetic perturbation

–  Oct mtg: Becoulet, JOREK group: Predict suppression at 80 kAt, n=2 for JET case, ELM mitigation in ITER at 35 kAt

•  Energy evenly spread in n=2,4,6,8 looks like continuous turbulence or very small ELMs, from non-linear interactions of multi-modes

•  Reduces P-B drive for any other single mode; No large ELM crash •  Tearing parity; produces additional islands

–  Oct mtg: Orain, JOREK group: Simulation of AUG n=2 case (at 10x expt res),

•  Small resonant braking, small change in ne (pumpout not seen) •  Amplification at kink m > nq harmonics




•  3.5 Explain mechanism for how local pedestal top transport stops expansion of pedestal width

•  3.6 Determine role of resonant vs non-resonant spectral components and q95 dependence of Sup/Mit

–  NEW: Latest developments from both Callen and LeConte propose mechanisms that would imply q-dependence

•  Callen: Magnetic flutter depends on strong kink response between well spaced rational surfaces

•  LeConte: Resonant current coupling of VF to equilibrium Er

–  Oct mtg: EAST, KSTAR high nu* better mitigation with strongly “non-resonant” spectra - Are these kink aligned?


Theory (Experimental Validation): Effects on Pedestal Structure and Transport

Theory: Effects on Pedestal Structure and Transport

•  4.1 Quantify effect of RMP on ped height and width versus EPED1.6 etc. – Consistent with IOS request

•  4.2 Quantify impact of RMP on core transport and H-factor - Consistent with IOS request

•  4.3 Quantify impact of RMP on divertor fluxes and plasma wall interaction including best available plasma response models –  Oct mtg: COMPASS particle flux lobes on divertor targets in L-mode

agree with vacuum modeling

•  4.4 Determine the best characteristic parameter of ELM Control, eg.: –  Oct mtg: AUG, DIII-D, MAST consensus strong edge kink-peeling plasma

response and edge kink aligned MP components required for mitigation

Pedestal and ITER


ITER 3D-MP Coil Set Performance Predictions

•  5.1 Model the performance of the ITER RMP coil set, calculate divertor/wall power loads including best available plasma response models, and optimize ITER coil operation

–  Oct mtg: M3D-C1 (Ferraro) survey of ITER coil capability at 90 kAt shows 4 metrics met for all but 2 scenarios, and sensitivity to reduced coil current

–  Oct mtg: MARS-F,Q (Y-Q Liu) analysis shows Xpt displacement and edge island size metrics maximized with optimized phasing of 3 coil rows

•  9MA scenario at 45 kAt possible rotation braking, 15MA scenario at up to 45 kAt no core braking

–  Oct mtg: ASCOT modeling (Kurki-Suonio) of FI loss with RMP shows MARS-F plasma response reduces peak heat loads (more so in 9MA scenario)

ITER


Rapid Transition to Improved Pedestal Pressure Seen in DIII-D DN QH-mode Plasmas with NB Torque Ramp Down

•  Edge pressure pedestal height and width show stepwise increase as rotation drops due to decrease of neutral beam torque

•  Improved pedestal collapses when torque is increased again

•  Electron pedestal pressure increases ~60%, width increases ~45%, energy confinement H98y2 increases ~40%

•  Transition is associated with –  Changes in structure of edge

Er well –  Increased density and broadband

MHD fluctuations

•  These plasmas still operate without ELMs Burrell, Xi Chen,

APS15 (PoP), TTF16


Magnetic Probes Show Increased Broadband MHD Always Occurs at Transition to Wide Pedestal

•  Coherent EHO does not inhibit wide pedestal

Bθ

~ •

Burrell, Xi Chen, APS15, TTF16

•  Te and ne pedestals wider and higher •  ExB shearing rate decreased for r>0.9

but increased for r < 0.9 •  Increased edge transport allows

higher stable pedestal pressure


ITPA IOS TG (Luce chair) Requested Input on Models for Pedestal and ELM Control Effects

•  Request #1: Pedestal height and width predictions for ITER ELMing DT scenarios (6 months - Now)

•  Request #2: Effects of ELM mitigation strategies (6-12 months = by IAEA)

•  Request #3: Dependence of pedestal height and width on working gas (6 months = Now)

•  Request #4: Pedestal behavior on entry to and exit from burn (12-18 months = by April 2017)

•  Request #5: Pedestal behavior current rampup and rampdown (12-18 months = by April 2017)

•  Request #6: Zeff dependence of the pedestal height and width in DT operation (12-18 months = by April 2017)


Discussion: ITPA IOS Models for ELM Control Effects

Request #2: Effects of ELM mitigation strategies (6-12 months = by IAEA): for all techniques need models for:

–  Effect on density: fueling (pellet pacing) or pumpout (RMP) –  Energy confinement degradation if any: usually not severe; quantify? –  Particle throughput: potential issue for D2 pellets, less for solid pellets? –  Impurity accumulation: quantify effect on taup* for high-Z impurities –  As functions of:

•  ELM size •  Pedestal parameters or proximity to stability boundaries

•  RMP ELM Mitigation or Suppression: need models for –  Threshold perturbation strength required vs operating parameters

•  Pellet ELM Pacing: need models for –  Required pellet frequency, size, velocity

•  QH-mode, I-mode or Other ELM Control Techniques –  Access and sustainment requirements – internal plasma modes

pep itpa working group on rmp elm control: 11 status...

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